The invention relates to an arrangement for the transmission of synchronous television composite signals separated into luminance and chrominance component signals. Coders are provided which convert the luminance signal y and chrominance signals u, v into variable-length code words. Decoders are also provided which reconvert the variable-length code words.
A coding with variable code word lengths is known from the NTG-Fachberichte 84, "Neue Aspekte der Informations- und Systemtheorie", VDE-Verlag GmbH, Berlin-Offenbach, 1983, pages 219 through 225, incorporated herein by reference. Given such a coding, the word synchronization can be lost given the occurrence of transmission errors. This means that the code words are no longer separable at the receive side. If such coded luminance and chrominance signals were interlaced word-wise, then the consequences of a bit error would affect both signal types given the occurrence of a bit error.
A transmission system for television signals is known from the reference "Review of the Electrical Communication Laboratories", Vol. 27, No. 11-12, Nov.-Dec. 1979, pages 1095-1112, particularly FIG. 12, incorporated herein by reference. Given this system, a first quantizer generates four-place or eight-place DPCM code words depending on the coding rule. The changeover controller at the transmit side counts the eight-place DPCM code words appearing within a measuring time span and engages a different quantizer after it has reached a certain number, this different quantizer generating four-place DPCM code words. Given this system, a switch is provided to allow the quantizer to have a coarser characteristic given a pending buffer overflow.
A further transmission system is known from the German published application No. OS 33 14 384, incorporated herein by reference, wherein a first quantizer for code words having a length of up to six bits and a second quantizer for code words having a length of three bits are disposed in a DPCM loop. The quantizer for the next PCM code word pending at the input is selected after every switchover on the basis of the number of memory locations still existing.